X-ray CT systems and methods for creating tomographic recordings are generally known. In particular methods are known, with which the temporal resolution is doubled with the aid of two emitter/detector arrangements offset at an angle on a gantry compared with CT systems with one emitter/detector arrangement. However here both emitter/detector arrangements are operated with the same x-ray energy spectrum, so that the information obtained by way of the emitter/detector arrangements is consistent per se. If simultaneous scanning takes place with different x-ray energy spectra, the resulting projections can in principle be reconstructed into one image with high temporal resolution. However the different x-ray energy spectra used to obtain the projections result in images with disruptive artifacts.
In practice there is on the one hand a desire to obtain more information about the composition of the examination object by using different x-ray spectra when scanning with a two-emitter/detector arrangement than is possible when scanning with a single spectrum. At the same time a high level of temporal resolution is desirable, particularly during a cardiac examination, in which process the combination of these two requirements should not result in an increased dose burden.